// Partial implementation of binary-tree based set class similar to std::set.  
// The iterator increment & decrement operations have been omitted.
#ifndef ds_set_h_
#define ds_set_h_
#include <iostream>
#include <utility>

// -------------------------------------------------------------------
// TREE NODE CLASS 
template <class T>
class TreeNode {
public:
  TreeNode() : left(NULL), right(NULL) {}
  TreeNode(const T& init) : value(init), left(NULL), right(NULL) {}
  T value;
  TreeNode* left;
  TreeNode* right;
};

// -------------------------------------------------------------------
// TREE NODE ITERATOR CLASS
template <class T>
class tree_iterator {
public:
  tree_iterator() : ptr_(NULL) {}
  tree_iterator(TreeNode<T>* p) : ptr_(p) {}
  tree_iterator(const tree_iterator& old) : ptr_(old.ptr_) {}
  ~tree_iterator() {}
  tree_iterator& operator=(const tree_iterator& old) { ptr_ = old.ptr_;  return *this; }

  // operator* gives constant access to the value at the pointer
  const T& operator*() const { return ptr_->value; }
  // comparions operators are straightforward
  bool operator== (const tree_iterator& rgt) { return ptr_ == rgt.ptr_; }
  bool operator!= (const tree_iterator& rgt) { return ptr_ != rgt.ptr_; }

private:
  // representation
  TreeNode<T>* ptr_;
};

// -------------------------------------------------------------------
// DS_SET CLASS
template <class T>
class ds_set {
public:
  ds_set() : root_(NULL), size_(0) {}
  ds_set(const ds_set<T>& old) : size_(old.size_) { 
    root_ = this->copy_tree(old.root_); }
  ~ds_set() {
    this->destroy_tree(root_);
    root_ = NULL;
  }
  ds_set& operator=(const ds_set<T>& old) {
    if (&old != this) {
      this->destroy_tree(root_);
      root_ = this->copy_tree(old.root_);
      size_ = old.size_;
    }
    return *this;
  }

  typedef tree_iterator<T> iterator;

  int size() const { return size_; }
  bool operator==(const ds_set<T>& old) const { return (old.root_ == this->root_); }

  // FIND, INSERT & ERASE
  iterator find(const T& key_value) { return find(key_value, root_); }
  std::pair< iterator, bool > insert(T const& key_value) { return insert(key_value, root_); }
  int erase(T const& key_value) { return erase(key_value, root_); }
  
  // OUTPUT & PRINTING
  friend std::ostream& operator<< (std::ostream& ostr, const ds_set<T>& s) {
    s.print_in_order(ostr, s.root_);
    return ostr;
  }
  void print_as_sideways_tree(std::ostream& ostr) const {
    print_as_sideways_tree(ostr, root_, 0);
  }

  // ITERATORS
  iterator begin() const { 
    if (!root_) return iterator(NULL);
    TreeNode<T>* p = root_;
    while (p->left) p = p->left;
    return iterator(p);
  }
  iterator end() const { return iterator(NULL); }

private:
  // REPRESENTATION
  TreeNode<T>* root_;
  int size_;

  // PRIVATE HELPER FUNCTIONS
  TreeNode<T>*  copy_tree(TreeNode<T>* old_root) {
    if (old_root == NULL) 
      return NULL;
    TreeNode<T> *answer = new TreeNode<T>();
    answer->value = old_root->value;
    answer->left = copy_tree(old_root->left);
    answer->right = copy_tree(old_root->right);
    return answer;
  }

  void destroy_tree(TreeNode<T>* p) {
    if (!p) return;
    destroy_tree(p->right);
    destroy_tree(p->left);
    delete p;
  }

  iterator find(const T& key_value, TreeNode<T>* p) {
    if (!p) return iterator(NULL);
    if (p->value > key_value)
      return find(key_value, p->left);
    else if (p->value < key_value)
      return find(key_value, p->right);
    else
      return iterator(p);
  }

  std::pair<iterator,bool> insert(const T& key_value, TreeNode<T>*& p) {
    if (!p) {
      p = new TreeNode<T>(key_value);
      this->size_++;
      return std::pair<iterator,bool>(iterator(p), true);
    }
    else if (key_value < p->value)
      return insert(key_value, p->left);
    else if (key_value > p->value)
      return insert(key_value, p->right);
    else
      return std::pair<iterator,bool>(iterator(p), false);
  }
  
  int erase(T const& key_value, TreeNode<T>* &p) {
    if (!p) return 0;
 
    // look left & right
   if (p->value < key_value)
      return erase(key_value, p->right);
    else if (p->value > key_value)
      return erase(key_value, p->left);

    // Found the node.  Let's delete it
    assert (p->value == key_value);
    if (!p->left && !p->right) { // leaf
      delete p; p=NULL; 
    } else if (!p->left) { // no left child
      TreeNode<T>* q = p; p=p->right; delete q; 
    } else if (!p->right) { // no right child
      TreeNode<T>* q = p; p=p->left; delete q; 
    } else { // Find rightmost node in left subtree
      TreeNode<T>* &q = p->left;
      while (q->right) q = q->right;
      p->value = q->value;
      int check = erase(q->value, q);
      assert (check == 1);
    }
    return 1;
  }

  void print_in_order(std::ostream& ostr, const TreeNode<T>* p) const {
    if (p) {
      print_in_order(ostr, p->left);
      ostr << p->value << "\n";
      print_in_order(ostr, p->right);
    }
  }

  void print_as_sideways_tree(std::ostream& ostr, const TreeNode<T>* p, int depth) const {
    if (p) {
      print_as_sideways_tree(ostr, p->right, depth+1);
      for (int i=0; i<depth; ++i) ostr << "    ";
      ostr << p->value << "\n";
      print_as_sideways_tree(ostr, p->left, depth+1);
    }
  }
};

#endif